The existing structure of the 3rd Generation Mobile Communication System Partnership Project (hereinafter referred to as 3GPP) is shown in FIG. 1. The description of the 3GPP system structure shown in FIG. 1 is given below.
A User Equipment (hereinafter referred to as UE) 101 is a terminal device for receiving data. A Node B 102 is a node responsible for radio transmitting/receiving in a Radio Network Subsystem (RNS). A Controlling Radio Network Controller (hereinafter referred to as CRNC) 103 is a radio network controller which directly controls a Node B. The interface between a Radio Network Controller (hereinafter referred to as RNC) and the UE is known as the air interface. A Serving Radio Network Controller (hereinafter referred to as SRNC) 104 is a RNC which controls bearer information, such as the Radio Resource Control (hereinafter referred to as RRC) status. The interface between the SRNC and the CRNC is the interface known as Iur. A Gateway General Packet Radio Service (the General Packet Radio Service is hereinafter referred to as GPRS) Supporting Node (the Gateway GPRS Supporting Node is hereinafter referred to as GGSN) 105 and a Serving GPRS Supporting Node (hereinafter referred to as SGSN) 106 provide routing function for data transmission. The interface between the SGSN and the RNC is the interface known as lu. E-PDN 107 is an external public data network providing data source.
The system structure of the System Architecture Evolution (SAE) is illustrated in FIG. 2. The description of the SAE system structure shown in FIG. 2 is given below.
A User Equipment (hereinafter referred to as UE) 201 is a terminal device for receiving data. An EUTRAN 202 (also known as eNB), which is the radio access network of the evolution system SAE, is responsible for providing a LTE (Long Term Evolution) mobile phone with the access to the radio network. The eNB is also connected to a mobility management entity (MME) 203 of the mobile phone and a user plane entity (Serving Gateway) 204 via an interface S1. A MME 203 is responsible for managing mobile contexts and session contexts of the UE and for saving user information on security. Serving Gateway (Serving GW) 204 mainly provides functions of the user plane. An interface S1-MME is responsible for establishing a radio access bearer for the UE and forwarding messages from the UE to the MME via the radio access network. The combined function of the MME 203 and the Serving Gateway 204 is similar to that of the original SGSN 206. Both the MME and the Serving Gateway may be located at the same physical entity. A PDN Gateway 205 is responsible for functions like billing, lawful interception and the like. In addition, both the Serving Gateway and the PDN Gateway may be located at the same physical entity. The SGSN 206 is now configured to provide routing function for data transmission in the UMTS. The existing SGSN is configured to find out the corresponding Gateway GPRS Supporting Node (GGSN) based on an Access Point Name (APN). A HSS 207 is a home subscriber subsystem which is responsible for storing user information including the current location of the UE, the address of a serving node, user information on security, Packet Data Protocol (PDP) context activated by the UE and so on. PCRF 208 provides QoS policies and billing criteria via an interface S7.
In general, a user data stream passes through the PDN Gateway 205 to the Serving Gateway 204 which then transmits the data to the eNB where the UE locates using a GPRS Tunneling Protocol (GTP) channel. The eNB then transmits the data to a corresponding UE.
FIG. 3 shows the structure of the interface 51 in the SAE, where an EPC is a core network of the evolution. Each eNB is connected with a plurality of MMEs in a MME pool. Each eNB is further connected to a plurality of S-GWs in a S-GW Pool.
A HNB (including 3G HNB, LTE HNB and an HNB in another access system) is a Node B applied in a home and can be applied in such a site as a university, a company and so on. The HNB is a Plug-and-Play device, and can be of an open type and a closed subscriber group type. The difference between a HNB of the closed subscriber group type and a common macro base station lies in that typically not all the UEs are permitted to access the HNB. For instance, only UEs which belong to a user's home or are permitted by one of the family members to access the HNB are permitted to access the HNB of the home. For a HNB in a company, only the company's staff and its granted partners are permitted to access the HNB. A HNB group having the same access subscriber set (e.g., HNBs arranged in the same company) is referred to as a CSG (Closed Subscriber Group).
The structure of a 3G HNB is illustrated in FIG. 4, where a UTRAN includes a 3G HNB and a 3G HNB GW. The HNB and the HNB GW constitute a HNB RAN. The 3G HNB performs the functions of an original Node B and some functions of the RNC, such as RRC, RLC, MAC, etc. The 3G HNB GW, which is a node connected to the core network, includes the functions of a NNSF. The interface between the HNB and the HNB GW is known as Iuh. The 3G HNB GW accesses the core network via the lu interface.
The HNB or the HNB GW can perform the access control of the UE. The HNB or the HNB GW stores a list of UEs identity which the HNB is permitted to access. When the HNB RAN receives a message from UE, it is determined whether the UE is permitted to be accessed or not based on the UE's IMSI. If no IMSI is contained in the received message, the HNB RAN can transmit an identification request message to the UE. The UE'S IMSI can be obtained once a response message from the UE is received. There is no final conclusion on which one of the HNB and the HNB GW is more suitable to perform the access control of the UE. By far, most companies support a decision that the HNB GW should perform the access control of the UE, e.g., the access of the UE is permitted or not.
In existing communication systems, after a radio resource management entity (such as a HNB, a RNC or an eNB) receives a Radio Link Setup Request message from a UE, it is known that there is an emergency service based on the information element Establishment Cause in the message. However, the upper-layer node (e.g., a SGSN or a HNB GW) of the radio resource management entity does not know that the service to be accessed is an emergency service. Therefore, the upper-layer node of the radio resource management entity may perform the access control of the UE, which may result in a failure or delay of the access of the emergency service.